Variable radius spring disc for vehicle shock absorber

ABSTRACT

A shock absorber for a vehicle may include a piston and a valve disc assembly. The piston defines a plurality of passages extending through the piston between an upper working chamber and a lower working chamber of a fluid chamber. The valve disc assembly engages the piston and controls a flow of fluid between the upper working chamber and the lower working chamber through the plurality of passages. The valve disc assembly includes a variable radius spring disc among a plurality of discs. The variable radius spring disc has a varying outer radius. The valve disc assembly has a stiffness that varies circumferentially based on the variable radius spring disc such that an actuation of the valve disc assembly with respect to the piston varies circumferentially.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/000,990, filed on May 20, 2014. The entire disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present disclosure relates to shock absorbers. More particularly,the present disclosure relates to a valve disc assembly for controllingdamping characteristics of a shock absorber.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Shock absorbers are used in conjunction with automotive suspensionsystems to absorb unwanted vibrations that occur during driving. Toabsorb the unwanted vibrations, shock absorbers are generally connectedbetween the sprung portion (body) and the unsprung portion (suspension)of the automobile. A piston is located within a pressure tube of theshock absorber and the pressure tube is connected to the unsprungportion of the vehicle. The piston is connected to the sprung portion ofthe automobile through a piston rod which extends through the pressuretube.

The piston divides the pressure tube into an upper working chamber and alower working chamber, both of which are filled with hydraulic fluid.Through valving, the piston is able to limit the flow of the hydraulicfluid between the upper and the lower working chambers when the shockabsorber is compressed or extended. Accordingly, the shock absorber isable to produce a damping force that counteracts the vibration whichwould otherwise be transmitted from the unsprung portion to the sprungportion of the vehicle. In a dual tube shock absorber, a fluid reservoiror reservoir chamber is defined between the pressure tube and areservoir tube. A base valve is located between the lower workingchamber and the reservoir chamber to control the flow of fluid betweenthe lower working chamber and the reservoir chamber.

Shock absorbers have been developed to provide different dampingcharacteristics depending on the speed or acceleration of the pistonwithin the pressure tube. Because of the exponential relationshipbetween pressure drop and flow rate, it can be difficult to tune thedamping characteristic of the shock absorber between low and high pistonspeeds. Specifically, the valving at the piston and/or base valve isdesigned to close/open in one unilateral movement, thereby causing anabrupt change in damping between low and high piston speeds.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features. Thepresent disclosure relates to a shock absorber for a vehicle, and moreparticularly, to a valve disc assembly that controls the flow of fluidbetween an upper working chamber and a lower working chamber at varyingpiston speeds. The shock absorber includes a pressure tube that definesa fluid chamber, a piston that is disposed within the fluid chamber, anda valve disc assembly that engages with the piston. The piston dividesthe fluid chamber into an upper working chamber and a lower workingchamber, and defines a plurality of passages that extend through thepiston between the upper working chamber and the lower working chamber.

The valve disc assembly controls the flow of fluid between the upperworking chamber and the lower working chamber. The valve disc assemblyincludes a variable radius spring disc among a plurality of discs. Thevariable radius spring disc has an outer radius that circumferentiallyvaries along an outer perimeter of the variable radius spring disc. Thevalve disc assembly has a stiffness that varies in relation to acircumference of the variable radius spring disc such that an actuationof the valve disc assembly with respect to the piston variescircumferentially.

In a feature of the present disclosure, as fluid pressure increases inthe plurality of passages, the valve disc assembly may deflect away fromthe piston along a direction that corresponds to an increase of theouter radius of the variable radius spring disc, and as fluid pressuredecreases in the plurality of passages, the valve disc assembly mayactuate to seal the passages along a direction that corresponds to adecrease of the outer radius of the variable radius spring disc.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only, and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic representation of a typical automobile thatincorporates at least one shock absorber;

FIG. 2 is a side partial cross-sectional view of a shock absorber;

FIG. 3 is an enlarged cross-sectional view of a piston assembly of theshock absorber;

FIG. 4 is an enlarged cross-sectional view of a valve disc assembly forcontrolling fluid through compression passages;

FIG. 5 is an exploded view of the valve disc assembly of FIG. 4;

FIG. 6 is a perspective view of a variable radius spring disc of thevalve disc assembly;

FIG. 7 is a top view of the variable radius spring disc and a soliddisc;

FIG. 8 is a perspective view of a variable radius spring disc in asecond embodiment; and

FIG. 9 is a perspective view of a variable radius spring disc in a thirdembodiment.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

The present disclosure will now be described more fully with referenceto the accompanying drawings. Referring now to the drawings in whichlike reference numerals designate like or corresponding parts throughoutthe several views, FIG. 1 illustrates a vehicle 10 incorporating asuspension system with shock absorbers having a variable radius springdisc in accordance with the present disclosure. The vehicle 10 includesa rear suspension 12, a front suspension 14, and a body 16. The rearsuspension 12 has a transversely extending rear axle assembly (notshown) adapted to operatively support the vehicle's rear wheels 18. Therear axle assembly is operatively connected to the body 16 by means of apair of shock absorbers 20 and a pair of helical coil springs 22.Similarly, the front suspension 14 includes a transversely extendingfront axle assembly (not shown) to operatively support the vehicle'sfront wheels 24. The front axle assembly is operatively connected to thebody 16 by means of a second pair of shock absorbers 26 and by a pair ofhelical coil springs 28.

The shock absorbers 20 and 26 serve to dampen the relative motion of theunsprung portion (i.e., the front and rear suspensions 12 and 14,respectively) and the sprung portion (i.e., the body 16) of the vehicle10. While the vehicle 10 has been depicted as a passenger car havingfront and rear axle assemblies, the shock absorbers 20 and 26 may beused with other types of vehicles or in other types of applicationsincluding, but not limited to, vehicles incorporating independent frontand/or independent rear suspension systems.

Referring now to FIG. 2, the shock absorber 20 is shown in greaterdetail. While FIG. 2 illustrates only shock absorber 20, it is to beunderstood that the shock absorber 26 includes the same components asthe shock absorber 20. The shock absorber 26 only differs from the shockabsorber 20 in the manner in which it is adapted to be connected to thesprung and unsprung portions of the vehicle 10. Furthermore, while theshock absorber 20 is depicted as a dual-tube shock absorber, shockabsorber 20 may also be a mono-tube shock absorber.

The shock absorber 20 comprises a pressure tube 30, a piston assembly32, a piston rod 34, a reservoir tube 36, and a base valve assembly 38.The pressure tube 30 defines a working chamber 42. The piston assembly32 is slidably disposed within the pressure tube 30, and divides theworking chamber 42 into an upper working chamber 44 and a lower workingchamber 46. A seal 48, which is shown in FIG. 3, is disposed between thepiston assembly 32 and the pressure tube 30 to permit sliding movementof the piston assembly 32 with respect to the pressure tube 30 withoutgenerating undue frictional forces as well as sealing the upper workingchamber 44 from the lower working chamber 46.

The piston rod 34 is attached to the piston assembly 32 and extendsthrough the upper working chamber 44 and through an upper end cap 50which closes the upper end of pressure tube 30. The end of the pistonrod 34 opposite to the piston assembly 32 is adapted to be secured tothe sprung portion of vehicle 10.

Valving within the piston assembly 32 controls the movement of fluidbetween the upper working chamber 44 and the lower working chamber 46during movement of the piston assembly 32 within the pressure tube 30.Because the piston rod 34 extends only through the upper working chamber44 and not the lower working chamber 46, movement of the piston assembly32 with respect to the pressure tube 30 causes a difference in theamount of fluid displaced in the upper working chamber 44 and the amountof fluid displaced in the lower working chamber 46. The difference inthe amount of fluid displaced flows through the base valve assembly 38,the piston assembly 32, or a combination thereof.

The reservoir tube 36 surrounds the pressure tube 30 to define a fluidreservoir chamber 52 located between the tubes 30 and 36. The base valveassembly 38 is disposed between the lower working chamber 46 and thereservoir chamber 52 to control the flow of fluid between the chambers46 and 52. When the shock absorber 20 extends in length, fluid will flowfrom the reservoir chamber 52 to the lower working chamber 46 throughthe base valve assembly 38. Fluid may also flow from the upper workingchamber 44 to the lower working chamber 46 through the piston assembly32. When the shock absorber 20 compresses in length, an excess of fluidis removed from the lower working chamber 46. Specifically, fluid flowsfrom the lower working chamber 46 to the reservoir chamber 52 throughthe base valve assembly 38.

Referring now to FIG. 3, the piston assembly 32 comprises a piston body60, a compression valve assembly 62, and a rebound valve assembly 64.The piston body 60 defines a plurality of compression fluid passages 66and a plurality of rebound fluid passages 68, and includes a compressionvalve land 70 and a rebound valve land 72. The compression fluidpassages 66 include an inlet 74 and an outlet 76. The rebound fluidpassages 68 include an inlet 78 and an outlet 80. The compression fluidpassages 66 and the rebound fluid passages 68 fluidly couple the upperworking chamber 44 and the lower working chamber 46.

The piston body 60 abuts with the compression valve assembly 62, whichabuts with a shoulder 82 formed on the piston rod 34. The piston body 60also abuts with the rebound valve assembly 64, which is retained by aretaining nut 84. The retaining nut 84 and a retaining nut 86 securepiston body 60 and valve assemblies 62 and 64 to piston rod 34.

The compression valve assembly 62 includes a retainer 90, one or morespacers 92, and a valve disc assembly 94. The retainer 90 is disposedabove the piston body 60 and abuts with the shoulder 82. The spacers 92are disposed between the valve disc assembly 94 and the retainer 90 andbetween the valve disc assembly 94 and the piston body 60. The valvedisc assembly 94 abuts with the compression valve land 70 and closes theoutlet 76 of the compression fluid passages 66.

The rebound valve assembly 64 also includes a retainer 100, one or morespacers 102, and a valve disc assembly 104. The retainer 100 is disposedbelow the piston body 60 and abuts with the retaining nut 84. Thespacers 102 are disposed between the valve disc assembly 104 and theretaining nut 84 and between the valve disc assembly 104 and the pistonbody 60. The valve disc assembly 104 abuts with the rebound valve land72 and closes the outlet 80 of rebound fluid passages 68.

In the example embodiment, the damping characteristics for both rebound(extension) and compression for the shock absorber 20 are determined bythe piston assembly. More particularly, the piston assembly 32 isprovided as a fully displaced valving that includes valving for mid/highfluid speeds and an independent valving for low piston speeds (i.e., lowhydraulic fluid flow or low fluid speed). During mid/high level speed,damping is controlled by the deflection of the valve disc assembly 94 ofthe compression valve assembly 62 and the valve disc assembly 104 of therebound valve assembly 64. During low level speeds, damping iscontrolled by bleed passages.

In an alternative embodiment, the damping characteristics for reboundand compression of the shock absorber 20 can be determined by acombination of a piston assembly and a base valve assembly. Moreparticularly, in a rod displaced valving, the base valve assembly mayinclude a plurality of discs that control the flow fluid between thereservoir chamber and the lower working chamber. For example, duringmid/high piston speed, damping can be controlled by the base valveassembly and valving at the piston. At low piston speeds, the base valveassembly can include a bleed passage to control the flow of fluid duringcompression, and the rebound valve assembly at the piston may include ableed passage to control the flow of fluid during rebound.

Referring to FIGS. 4-5, an example of the valve disc assembly 94 of thecompression valve assembly 62 is presented. The valve disc assembly 94includes a plurality of discs 200 that control the flow of fluid betweenthe lower working chamber 46 and the upper working chamber 44. The valvedisc assembly 94 may be biased against the piston body 60 to seal thecompression fluid passages 66. The valve disc assembly 94 includes anorifice disc 204, one or more solid discs 208, and a variable radiusspring disc 212. The plurality of discs 200 each define a center bore218, and are concentrically disposed with each other about the pistonrod 34.

In the example embodiment, the orifice disc 204, the solid discs 208,and the variable radius spring disc 212 are positioned at thecompression valve land 70 of the piston body 60 with the orifice disc204 abutting against the compression valve land 70 of the piston body60. Alternatively, the orifice disc 204 may be eliminated and a bleedorifice (not shown) may be disposed within the compression valve land70. Accordingly, the solid discs 208 and the variable radius spring disc212 may be positioned at the compression valve land 70 with one of thesolid discs 208 abutting against the compression valve land 70 of thepiston body 60.

The orifice disc 204 defines one or more orifices 220, and may also bereferred to as a bleed disc. The orifice 220 forms a bleed passagereferenced by arrow 224 for allowing fluid to flow between the upperworking chamber 44 and the lower working chamber 46 at low pistonspeeds. The bleed passage 224 is open during compression and rebound,thereby allowing fluid to flow from the lower working chamber 46 to theupper working chamber 44, and vice versa.

A first solid disc 208A from among the one or more solid discs 208 isdisposed over the orifice disc 204 to cover the orifices 220 of theorifice disc 204. In the example embodiment, the variable radius springdisc 212 is positioned after the first solid disc 208A. Moreparticularly, the plurality of discs 200 are arranged such that one ormore solid discs 208 are disposed between the orifice disc 204 and thevariable radius spring disc 212. Accordingly, while the exampleembodiment illustrates one solid disc 208, more than one solid disc 208may be located between the orifice disc 204 and the variable radiusspring disc 212.

FIGS. 6 and 7 depict the variable radius spring disc 212. The variableradius spring disc, which may also be referred to as a helical disc, hasan inner radius R_(I) and an outer radius R_(O). The inner radius R_(I)is a fixed radius that extends from a center point CP to an innerperimeter 226 that defines the center bore 218. The outer radius R_(O)extends from the center point CP to an outer perimeter 228 and variesalong the outer perimeter 228. Specifically, the variable radius springdisc 212 includes a maximum outer radius R_(OMAX) and a minimum outerradius R_(OMIN). The outer radius R_(O) continuously changes between themaximum outer radius R_(OMAX) and the minimum outer radius R_(OMIN) suchthat the variable radius spring disc 212 is asymmetrical. With thevarying outer radius R_(O), the variable radius spring disc 212 has aspiral like configuration in which the outer radius R_(O) decreases andvaries from the maximum outer radius R_(OMAX) to the minimum outerradius R_(OMIN).

Similar to the valve disc assembly 94 of the compression valve assembly62, the valve disc assembly 104 of the rebound valve assembly 64 mayinclude the plurality of discs 200, and more particularly, the variableradius spring disc 212. While the valve disc assemblies 94 and 104 aredescribed as having the same set of plurality of discs 200, the valvedisc assemblies 94 and 104 may have a different number of discs that canbe arranged in various suitable manners.

During a compression stroke, fluid in the lower working chamber 46 ispressurized and flows from the lower working chamber 46 to thecompression fluid passages 66. The rebound valve assembly 64 restrictsthe flow of fluid through rebound fluid passages 68. At low fluidspeeds, a controlled amount of fluid flows between the upper workingchamber 44 and the lower working chamber 46 through the bleed passage224 defined by the orifice disc 204.

As fluid pressure in the lower working chamber 46 increases, the fluidin the compression fluid passages 66 exerts a force against the valvedisc assembly 94, such that the orifice disc 204 exerts a pressure ontothe solid disc 208, and the solid disc 208 exerts a pressure onto thevariable radius spring disc 212. As described in detail below, thestiffness of the valve disc assembly 94 varies in relation to thecircumference of the valve disc assembly 94. Accordingly, the fluidpressure required to overcome a force associated with the stiffnessvaries circumferentially. When the force is exceeded, the valve discassembly 94 deflects to allow fluid to flow past the valve disc assembly94. Thus, fluid flows through the compression fluid passages 66 into theupper working chamber 44.

During a rebound stroke, fluid in the upper working chamber 44 ispressurized, and fluid flows from the upper working chamber 44 to therebound fluid passages 68. The compression valve assembly 62 restrictsthe flow of fluid through the compression fluid passages 66 during therebound stroke. Fluid flowing through the rebound fluid passages 68 iscontrolled by the rebound valve assembly 64. Prior to the deflection ofthe rebound valve disc assembly 104, a controlled amount of fluid flowsfrom the lower working chamber 46 to the upper working chamber 44through a bleed passage that provides damping at low fluid speeds. Thefluid pressure within rebound fluid passages 68 eventually opens therebound valve assembly 64 by deflecting the valve disc assembly 104.

The variable radius spring disc 212 promotes the asymmetrical stiffnessto control the opening/closing of the valve disc assemblies 94 and 104.More particularly, by having the variable radius spring disc 212, thevalve disc assemblies 94 and 104 gradually open/close in an analogwraparound manner. The operation of the variable radius spring disc 212is described with reference to the valve disc assembly 94, and is alsoapplicable to the valve disc assembly 104.

With reference to FIG. 7, the variable radius spring disc 212 isillustrated with the solid disc 208A, which is disposed between thevariable radius spring disc 212 and the valve land 70. The surface areaof the solid disc 208A that engages with the variable radius spring disc212 varies in relation to the circumference of the variable radiusspring disc 212. Accordingly, the solid disc 208A is subjected to astiffness that varies circumferentially. As an example, sections of thesolid disc 208A that align with the minimum outer radius R_(OMIN) of thevariable radius spring disc 212 require less pressure to deflect thansections of the solid disc 208A that align with the maximum outer radiusR_(OMAX).

Accordingly, as fluid pressure increases, sections of the solid disc208A that are not covered by the variable radius spring disc 212 beginto open. For instance, the solid disc 208A may begin to deflect along anouter perimeter of the solid disc 208A starting with an area adjacent tothe minimum outer radius R_(OMIN) of the variable radius spring disc212. The solid disc 208A may continue to deflect toward a sectionadjacent to the maximum outer radius R_(OMAX).

As pressure continues to build, sections of the solid disc 208A that arecovered with the variable radius spring disc 212 begin to open. Forexample, covered portions of the solid disc 208A may begin to deflectaway from the piston body 60 starting with a section having the leastsurface area coverage by the variable radius spring disc 212 to asection that has the most surface area coverage by the variable radiusspring disc 212.

The direction along which the solid disc 208A deflects during acompression or rebound stroke is represented by arrow 240. The variableradius spring disc 212 controls the deflection of the solid disc 208Asuch that the solid disc 208A circumferentially deflects away from thepiston body 60 in a wraparound manner. More particularly, the solid disc208A deflects along a direction that corresponds to the increasingradius of the variable radius spring disc 212.

While the wraparound deflection promoted by the variable radius springdisc 212 is described with respect to the solid disc 208A, the otherdiscs of the valve disc assembly 94 also deflect in a similar manner. Inparticular, the variable radius spring disc 212 controls the opening ofthe valve disc assembly 94 such that the portion of the valve discassembly 94 that aligns with the minimum outer radius R_(OMIN) of thevariable radius spring disc 212 begins to deflect away from the valveland 70 before the portion that aligns with the maximum outer radiusR_(OMAX). Due to the spiral configuration of the variable spring disc,the amount of deflection of the valve disc assembly 94 may vary suchthat the portion of the valve disc assembly 94 that aligns with theminimum outer radius R_(OMIN) may deflect more than the portion of thevalve disc assembly 94 that aligns with the maximum outer radiusR_(OMAX).

As fluid pressure in the lower working chamber 46 decreases, the forceexerted against the valve disc assembly 94 by the fluid in thecompression fluid passages 66 decreases. Specifically, the valve discassembly 94 closes the compression fluid passages 66 when the force ofthe valve disc assembly 94 overcomes the pressure exerted by the fluidin the compression fluid passages 66. Similar to the opening of thevalve disc assembly 94, the variable radius spring disc 212 controls thevalve disc assembly 94 such that the discs 200 gradually close thecompression fluid passages 66 in a wraparound manner. For example, aspressure reduces, the portion of the valve disc assembly 94 that alignswith the maximum outer radius R_(OMAX) of the variable radius springdisc 212 begins to return to an un-deflected state to rest against thevalve land 70 of the piston body before the portion that aligns with theminimum outer radius R_(OMIN). The valve disc assembly 94 continues toseal against the valve land 70 in a wraparound manner in a directionthat corresponds to the decreasing radius of the variable radius springdisc 212. The direction along which the valve disc assembly 94 begins toclose the compression fluid passages 66 is represented by arrow 244 inFIG. 7.

The variable radius spring disc 212 has a paisley or tear drop likeshape in which the outer radius continuously varies. The variable radiusspring disc may have other suitable shapes in which the outer radiusvaries between a maximum outer radius and a minimum outer radius. Forexample, FIGS. 8 and 9 illustrate a variable radius spring disc 300 anda variable radius spring disc 400, respectively. The variable radiusspring discs 300 and 400 each have a maximum outer radius R_(OMAX) and aminimum outer radius R_(OMIN). The variable radius spring disc 300 hasan outer perimeter 304, and the variable radius spring disc 400 has anouter perimeter 404. The variable radius spring discs 300 and 400perform in a similar manner to the variable radius spring disc 212 asdescribed herein.

The variable radius spring disc promotes an analog opening/closing ofthe valve disc assembly 94 and not a digital opening/closing in whichthe discs move all at once to fully open or fully close the flow offluid between the lower working chamber 46 and the upper working chamber44. By having an analog opening/closing, the damping characteristic ofthe shock absorber can be controlled between low speed and high speedoperations, thereby improving the steering and handling of the vehicle.Furthermore, the gradual wrap around opening/closing of the valve discassembly 94 prevents the discs 200 from blowing off or returning all atonce, thereby improving noise, harshness, and vibration qualities of theshock absorber.

While the variable radius spring disc is described as being part of thevalve disc assembly for both the compression valve assembly and therebound valve assembly, the variable radius spring disc can provide forone valve assembly and not the other valve assembly. In addition, thevariable radius spring disc may also be included in a base valveassembly.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth, such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms, and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged to, connected to, or coupled to the other elementor layer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein interpreted accordingly.

What is claimed is:
 1. A shock absorber for a vehicle comprising: apressure tube defining a fluid chamber; a piston disposed within thefluid chamber, the piston dividing the fluid chamber into an upperworking chamber and a lower working chamber, the piston defining aplurality of passages extending through the piston between the upperworking chamber and the lower working chamber; and a valve disc assemblysupported on the piston and controlling a flow of fluid between theupper working chamber and the lower working chamber through theplurality of passages, the valve disc assembly including a variableradius spring disc among a plurality of discs, wherein the variableradius spring disc has an outer radius that increases continuously andcircumferentially from a first circumferential point to a secondcircumferential point, along an outer perimeter of the variable radiusspring disc, and then makes a convex turn followed by a transition fromthe second circumferential point via a concave turn back to the firstcircumferential point, and the valve disc assembly creates a stiffnessthat varies in relation to a circumference of the variable radius springdisc such that an actuation of the valve disc assembly with respect tothe piston varies circumferentially.
 2. The shock absorber of claim 1wherein the variable radius spring disc has an asymmetrical shape. 3.The shock absorber of claim 1 wherein the variable radius spring dischas a maximum outer radius and a minimum outer radius, and a given outerradius measured from a center point to a given point along the outerperimeter has a value between the maximum outer radius and the minimumouter radius.
 4. The shock absorber of claim 1 wherein: the plurality ofdiscs of the valve disc assembly further includes an orifice disc andone or more solid discs, and the plurality of discs are arranged suchthat at least one of the one or more solid discs is disposed between theorifice disc and the variable radius spring disc.
 5. The shock absorberof claim 1 wherein: the plurality of discs actuate away from the pistonalong a first direction to allow fluid flow between the upper workingchamber and the lower working chamber, and actuate toward the pistonalong a second direction opposite to the first direction to preventfluid flow between the upper working chamber and the lower workingchamber, the first direction corresponds to a direction along which theouter radius of the variable radius spring disc increases, and thesecond direction corresponds to a direction along which the outer radiusof the variable radius spring disc decreases.
 6. The shock absorber ofclaim 1 wherein: the piston includes a support land thatcircumferentially extends along a surface of the piston, and theplurality of discs of the valve disc assembly further includes anorifice disc and one or more solid discs, the plurality of discs isdisposed at the support land and is arranged such that the orifice discis disposed on the support land and at least one of the one or moresolid discs is disposed between the orifice disc and the variable radiusspring.
 7. The shock absorber of claim 1 wherein: the variable radiusspring disc has a maximum outer radius and a minimum outer radius, andfluid pressure required to deflect the valve disc assembly from thepiston is greater at a portion of the valve disc assembly that alignswith the minimum outer radius than a portion of the valve disc assemblythat aligns with the maximum outer radius.
 8. The shock absorber ofclaim 1 wherein the stiffness of the valve disc assembly increases asthe outer radius of the variable spring disc increases.
 9. The shockabsorber of claim 1 wherein: the valve disc assembly deflects away fromthe piston along a direction that corresponds to an increase in theouter radius of the variable radius spring disc as fluid pressureincreases in the plurality of passages, and the valve disc assemblyactuates to seal the plurality of passages along a direction thatcorresponds to a decrease in the outer radius of the variable radiusspring disc as fluid pressure decreases in the plurality of passages.10. A shock absorber for a vehicle comprising: a pressure tube defininga fluid chamber; a piston disposed within the fluid chamber, the pistondividing the fluid chamber into an upper working chamber and a lowerworking chamber, the piston defining a plurality of passages extendingthrough the piston between the upper working chamber and the lowerworking chamber; and a valve disc assembly engaging the piston andcontrolling a flow of fluid between the upper working chamber and thelower working chamber through the plurality of passages, the valve discassembly including a plurality of discs, wherein the plurality of discsincludes a helical disc, wherein the helical disc has an outer radiusthat increases continuously and circumferentially from a first point toa second point, along an outer perimeter of the helical disc, and thenmakes a convex turn followed by a transition from the second point via aconcave turn back to the first point, and the valve disc assembly has astiffness that circumferentially varies based on the outer radius of thehelical disc such that the valve disc assembly circumferentiallyactuates in a wraparound manner along the piston.
 11. The shock absorberof claim 10 wherein the stiffness of the valve disc assembly isproportional to a surface area of the helical disc such that thestiffness increases as the surface area of the helical disc increases.12. The shock absorber of claim 10 wherein the stiffness of the valvedisc assembly increases as the outer radius of the helical discincreases and decreases as the outer radius of the helical discdecreases.
 13. The shock absorber of claim 10 further comprising: areservoir tube; and a base valve assembly, wherein the pressure tube ishoused in the reservoir tube, the pressure tube and the reservoir tubedefine a reservoir chamber, the base valve assembly controls the flow offluid between the lower working chamber and the reservoir chamber, andthe base valve assembly includes a second helical disc among a secondplurality of discs, the second helical disc has an outer radius thatvaries circumferentially along an outer perimeter of the second helicaldisc.
 14. The shock absorber of claim 10 wherein: the plurality of discsof the valve disc assembly further includes an orifice disc and one ormore solid discs, and the plurality of discs are arranged such that atleast one of the one or more solid discs is disposed between the orificedisc and the helical disc.
 15. The shock absorber of claim 10 wherein:the plurality of discs actuate away from the piston along a firstdirection to allow fluid flow between the upper working chamber and thelower working chamber, and actuate toward the piston along a seconddirection opposite to the first direction to prevent fluid flow betweenthe upper working chamber and the lower working chamber, the firstdirection corresponds to a direction along which the outer radius of thehelical disc increases, and the second direction corresponds to adirection along which the outer radius of the helical disc decreases.16. The shock absorber of claim 10 wherein the helical disc has amaximum outer radius and a minimum outer radius, and fluid pressurerequired to deflect the valve disc assembly at the maximum outer radiusof the helical disc is greater than at the minimum outer radius of thehelical disc.
 17. A shock absorber for a vehicle comprising: a pressuretube defining a fluid chamber; a piston disposed within the fluidchamber, the piston dividing the fluid chamber into an upper workingchamber and a lower working chamber, the piston defining a compressionpassage and a rebound passage, wherein the compression passage and therebound passage extend through the piston between the upper workingchamber and the lower working chamber; a compression valve assemblyengaging the piston, wherein the compression valve assembly controls aflow of fluid through the compression passage; and a rebound valveassembly engaging the piston and controlling a flow of fluid through therebound passage, wherein at least one of the compression valve assemblyand the rebound valve assembly includes a variable radius spring discamong a plurality of discs, the variable radius spring disc has an outerradius that continuously increases from a first point to a second pointalong an outer perimeter of the variable radius spring disc, and thenmakes a convex turn followed by a transition from the second point via aconcave turn back to the first point, and the at least one of thecompression valve assembly and the rebound valve assembly has astiffness that circumferentially varies based on the variable radiusspring disc.
 18. The shock absorber of claim 17 wherein the stiffness ofthe at least one of the compression valve assembly and the rebound valveassembly increases as the outer radius of the variable radius springdisc increases and decreases as the outer radius of the variable radiusspring disc decreases.
 19. The shock absorber of claim 17 wherein: theplurality of discs actuate away from the piston along a first directionto allow fluid flow between the upper working chamber and the lowerworking chamber, and actuate toward the piston along a second directionopposite to the first direction to prevent fluid flow between the upperworking chamber and the lower working chamber, the first directioncorresponds to a direction along which the outer radius of the variableradius spring disc increases, and the second direction corresponds to adirection along which the outer radius of the variable radius springdisc decreases.
 20. The shock absorber of claim 17 wherein the variableradius spring disc has an asymmetrical shape.